JPH02293089A - Method and apparatus for separating arsenic from waste water - Google Patents

Abstract

The process for removal of arsenic from waste waters is characterised by (A1) precipitation of the arsenic in the form of sparingly soluble calcium magnesium arsenates by addition of calcium compounds and magnesium compounds to the waste water at pH 2 to 12 and (A2) removal of the calcium magnesium arsenates and/or (B1) contacting the waste water with an ion exchanger at pH 2 to 12 and optionally (B2) regeneration of the ion exchanger after reaching the limit of the capacity and/or (C1) adsorptive removal of the aresenic by contacting the waste water with activated carbon at pH 2 to 11 and (C2) removal of the charged activated carbon alone or together with precipitation products. <??>The process permits removal of arsenic, in particular even in the case of waste waters that are difficult to treat and contain heavy metals such as lead, and also sulphate, to residual contents < 0.3 mg AS/l.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a highly efficient method and apparatus for separating arsenic from wastewater, particularly industrial wastewater. Conventional techniques and their problems Many industrial processes produce wastewater with more or less high arsenic content, but it has not been possible to separate arsenic from these wastewaters using conventional techniques. Glass glass (81! eikri
In the production of sta11) and crystal glass, molten glass (Glasschemelze) 2 is used as a fining agent.
weight! l! Q * diarsenic trioxide (A a 2 0 3
> has been added. Approximately 400 tons of arsenic is used annually for this purpose in West Germany. At the current level of technology, it is not possible to directly replace arsenic with a safe pond fining agent. Some of the added arsenic leaks from the molten glass, and about 0.2% by mass remains bonded to the glass matrix. During the purification process that treats the glass surface, arsenic is liberated again. This is called acid polishing (Siiurep).
o1iLur), that is, it also occurs when glass is treated with a sulfuric acid-hydrofluoric acid mixture, and a portion of it dissolves again. The same is true for glass polishing 1. Acid polishing water is approximately 40 to 100 mg A s /' i
! Glass Kenichi wastewater contains Noshimine (approximately 1 mg As/j) using the Rinjun method, and approximately 10 mg As/j using the circulation method.
Contains up to A s / 1. Arsenic-containing lyes are also produced during the production of non-ferrous metals. Dry type Ii! Water-soluble arsenic is present in the soda slag during smelting.
It is present in concentrations up to mg As/I.
Several mg/! even when preparing wet waste gas such as smoke desulfurization or extracting combustion residue! This results in a solution with a relatively high arsenic concentration in the range of . In addition, arsenic-containing wastewater is also generated during microchip manufacturing during etching with gallium arsenide.

Due to the high toxicity of arsenic, it is fundamentally necessary to reduce the arsenic content in wastewater as much as possible.

F, which was established by West Germany as part of the West German Interior Minister's environmental research plan.
raunhofer institutes fiirS
il+icatforschun8. Wiirzbu
An August 1986 research report in RG describes a study on the removal of arsenic from glass industry polishing wastewater. Such wastewater contains about 3 mg As/1 arsenic and about 10 mg P b,/i! Contains lead up to and including refrigerants, lubricants and surfactants (Tenside). The pH of such wastewater is between 7 and 8. In this research, various fundamentally possible methods of separating arsenic from wastewater are systematically investigated. Along with research on reducing arsenic on metal surfaces such as iron and zinc,
Research has been conducted to precipitate arsenic as arsenic sulfide, calcium arsenate, iron arsenate, magnesium ammonium arsenate, manganese arsenate, aluminum arsenate, and lead arsenate;
Only a resolution of less than 50% has been obtained.

Furthermore, research is being conducted on separation by adsorption using silica gel, alumina, and activated carbon containing titanic acid. The following can be confirmed from page 14 of the research report. That is, the addition of silica gel or activated carbon does not reduce the arsenic content in wastewater at all.

However, although a very small reduction in arsenic was observed with alumina, little has been said about its practical application.

In this systematic study, the only promising method for separating arsenic was to pre-mix As<II1) with As(V).
Precipitation with iron salts, with or without oxidation. By this method, in the case of suitable wastewater, 4 m
g/1 arsenic content can be reduced to below 0.1 rng/1. Acid laboratory wastewater from the glass industry contains up to 100 m g/1 arsenic in a strongly acidic solution, and can be prepared by simply dissolving arsenic sulfate in the acidic wastewater and precipitating the arsenic sulfide. It is possible to reduce the arsenic content by about half (see page 50 of the research report). This means that a sample with an initial arsenic content of approximately 15 mg/1 subsequently contains 6-7 mg/1 arsenic. In conclusion, from the level of technology mentioned above based on extensive research on arsenic separation (research report 5 mentioned above),
(see page 0), it can be seen that more laboratory research is needed to find technical means to separate arsenic.

From page 51 of this research report, it can be seen that no method has yet been established for removing arsenic from Sokenbukuro wastewater.

Fraunhofer InstiLuts fur
SiNicatforschung, Wjrzburg
Environmentally friendly technology in the production of lead glass and crystal glass - Removal of arsenic from polishing wastewater (Umwel)
! Lfreundliche Techno/ogie
n beder llerste1l1ung von
BIleikrisLau undκriztal'
1gfas-Entferr+ungvon Arse
nausSchReirereiabwasser)
In the publication titled , a method is described for separating arsenic from wastewater by producing iron arsenate and co-precipitating it in iron hydroxide precipitation according to the following reaction formula. Fe” + 3H20 →Fe (OH)3↓+3I{
゜F e ” + A s 04 code -+Fe
AsO < ↓ Neutralize with a suspension of calcium hydroxide while preventing a drop in pH with a constant iron sulfate solution.

At this time, sulfate ions precipitate as calcium sulfate.

This method can reduce arsenic content to less than 0.1 mg71 only in the case of polishing wastewater that contains a small amount of arsenic.
For example, it cannot be applied to wastewater from acid polishing processes. In this case, only about 50% of the arsenic contained is separated.

Handling and removal of iron sludge (Behand?nH
und BeseiLiFlung von Sk.
oroditschfa1) and title Dingru ＾Ding V-VKS-Merkblatt M 3 5
2 (April 1987)
It is stated as follows: That is, pyrometallurgical smelting (Skorod i L = iron arsenate FeAs) with a concentration of 1000-4000 mg / 1 in sulfuric acid solution
The water-soluble arsenic from ○,) was converted to As(V) with chlorine, and iron salt was added at 60-70°C and pH below 1, followed by carefully reducing the pH to <2-2 with calcium hydroxide. 2 5
and precipitate it as iron arsenate. Banfret I. makes no statement as to the extent of precipitation or the residual concentration of dissolved arsenic. The eluate contained 0. 3
~2 mg/1 As, 50-300 mg,-'
1 Cu, 100-300 mg/1 Zn, 1-3 m
g/1 Pb, o. 1-1 mg// of Fe and a CI of approximately 500 mg/1 are found.

What is the content of sulfate and calcium? [It is closely related to the solubility of calcium acid. Banfret 1. also states that neither alkaline reactions nor j-base reactions should occur in order not to increase the solubility of arsenic.

The separation of arsenic from arsenic-containing wastewater by the aforementioned method of precipitating trivalent arsenic as iron arsenate, with or without prior oxidation, is further described in DE 3632138. A1
and DE3633066A1.

Separation of arsenic from wastewater by precipitation of iron arsenate is applicable only to certain suitable wastewaters and is not a suitable method for the isolation of arsenic in its entirety.

Furthermore, DE 3637643A1 describes a method for removing arsenic from aqueous solutions. In other words, As (■) is changed to As (
This is a method in which wastewater is oxidized to V), then a water-soluble polymer anion exchange fat is added, and the wastewater is subjected to pressure using a membrane.

In this method arsenic is concentrated on the membrane. As the anion exchange resin used in this method, for example, a polymer having a molecular weight of 30,000 to 100,000, such as polyethyleneimine, has an exclusion limit (^ussch/uβgrenze>
It is used in combination with a 10' membrane. in this case,
Although the arsenic concentration in the clarified solution is not higher than 2 mg / 1, this method can only be used in one stage. The If method used here is, in principle, not suitable for application on an industrial scale.

Problems to be Solved by the Invention The present invention aims to solve the above-mentioned technical problems and provide a method and an apparatus that can be applied to industrial wastewater for the purpose of separating arsenic with high efficiency. By,
Arsenic can be separated and brought to a final concentration depending on the formulation, practically independent of the origin of the respective wastewater. In doing so, the invention starts from materials that are cheap and fully available, their products must not cause environmental problems, and at the same time the invention is very economical in terms of energy and material consumption. It has to be something.

The invention is also particularly suitable for very difficult wastewaters.

These objects were solved by claims 1.18 and 25.

The claims in question relate to superior particulars.

Means for solving the problem The method according to the invention for the separation of arsenic from wastewater comprises:
This method is characterized by the following methods. (^1) p in wastewater
H 2-12, preferably 9-11, precipitation time about 10
precipitating arsenic in the form of sparingly soluble calcium-magnesium arsenate by adding a compound of calcium and magnesium in ~60 minutes, preferably about 30 minutes;
and (A2) separation of calcium arsenate mago, sium,
and/or (B1) waste water with an ion exchange resin, preferably a strongly basic anion exchange resin, with a pH of 2 to 12, preferably 7 to 1.
1.5 and possibly (I12) load limits (Be1adungsgrenz
and/or (C1) contacting the wastewater with activated carbon at a pH of 2 to 11, preferably 2 to 4, to adsorb arsenic; and (C2) adsorbing the arsenic. separation of activated carbon alone or together with precipitated products.

Due to a suitable pH value of the alkaline region and a suitable excess of magnesium compound, magnesium hydroxide is precipitated simultaneously during the precipitation of treatment (A1), which has a favorable influence on the separation result.

Separation of arsenic by adsorption in treatment (C1) f) H31
or pH 1.1. The device according to the invention, which is particularly suitable for carrying out the method described above, is mainly characterized by the following construction, depending on the reaction route.

An oxidation and precipitation reactor for precipitating calcium magnesium arsenate, which can be connected with a storage tank for acid j arsenate, a storage tank for calcium compounds and a storage tank for magnesium compounds by conduits as necessary. a pH regulator, and a fractionator for distributing precipitated calcium magnesium arsenate from the wastewater, and/or an adsorption reactor for contacting the wastewater with activated carbon, and/or
Or an ion exchanger and, depending on the location, a regeneration facility.

Activated carbon, alumina (Tonerde) or aluminum oxide as well as silica gel are known as adsorbents for the adsorptive separation of arsenic in the state of the art, but these are not particularly suitable. In addition, adsorption of arsenic onto freshly precipitated magnesium hydroxide is also possible in principle. Freshly precipitated water! i
-(According to the literature, 1 g of hismagnesium can adsorb 125 mg of arsenic. Because of this adsorption capacity, magnesium hydroxide was used in ancient times as an antidote for arsenic poisoning.

As mentioned above, current technology allows arsenic to be precipitated from aqueous solutions as arsenic sulfide, calcium arsenate, iron arsenate, manganese arsenate, lead arsenate, and magnesium ammonium arsenate. However, these precipitation reactions are not suitable for large-scale arsenic-containing wastewater for the reasons mentioned above. moreover,
Ferric arsenate Skorodit, Sinp&isit and Ferrisimp1) isit must be decomposed with a base and completely dissolved in acid.As for the solubility of calcium arsenate, there is a wide variety in the literature, as seen in Table 1 below. The value is displayed (Gme
1in, Handbuch der anorgan
iscl+enCbemie. Tell B.
8. ＾uf1age, VerfaH
Chcmie Meinheim 1 9 5 6 >.

Table 1 C = z ) (A s○+) 2 ・8 H 20
gives up to 3% arsenic acid aqueous solution. basic a
3 Calcium Ca (AsO+)z Ca (OH)
2 becomes extremely difficult to dissolve in water.

Therefore, calcium arsenate has a solubility in the range of 60 to 200 mg/1, which means that calcium arsenate has a solubility in the range of about 2Q to 70 m
equivalent to g / 1 arsenic. Calcium salts are not suitable for precipitating arsenic from wastewater. Is its solubility lowered by the addition of zinc ions, heavy metal ions or fluoride or fluoride silk? but without taking into account the problems caused by such additions:
As a result, it is not possible to significantly reduce the solubility of calcium arsenate. Furthermore, from the literature, although it is not related to Motora wastewater,
It is found that calcium ammonium arsenate and magnesium ammonium arsenate are poorly soluble.

As can be seen from the techniques described so far, calcium 1 arsenate and magnesium have not been taken into account in the separation of arsenic from wastewater.

The method of the invention is carried out under acidic or alkaline conditions, for example CaO. , MgO2 or H20
■ As (I [[)
is preferably oxidized to As(V). At that time, H202, which becomes water due to acid 1, is particularly crushed.
．． The oxidation is preferably carried out at a pH in the acidic range.

This reaction can be carried out simultaneously with the precipitation of calcium magnesium arsenate and also before these precipitation reactions.

When the wastewater being handled contains sulfate ions that must be separated, these are added to the wastewater as Ca(OH).
z can be added to precipitate calcium sulfate. At this time, before step 1f (A1), C a S O
It is best to carry out these reactions at pH 3±1 if the + is to be precipitated. If precipitating CaSO+ is performed before treatment (B1> or (C1) and especially after treatment (A2), an adjustment to p}13±1 or 8.0 to 110 gives excellent results. It will be done.

As mentioned above, C 21 SO . Alternately or after the separation of the sulfates by precipitation of the wastewater, highly reactive i! ! By adding hyaluminum and/or calcium aluminate, especially alumina cement, the sulfate can be separated by precipitation of sparingly soluble calcium aluminate sulfate. At this time, Ca(01{)2
3 In addition, the pH must be kept constant in the range of 11.2 to 11 S. Milk of lime (Ca(O
H) When preliminary precipitation is carried out by z), the arsenic contained in the wastewater remains in solution;N. This phenomenon is particularly important.
This is because approximately 75-80% of the total sludge produced as CaSO+ can be separated at this stage, especially in the case of wastewaters with high sulfate content or concentrated wastewaters, which include very small amounts of sludge. It just contains heavy metals and especially arsenic. Therefore, such sludge can be classified as ordinary waste (Deponien) or construction waste% (B
auschuLtdeponien) can also be used. If necessary, the arsenic contained in the press water can also be removed by washing at this stage, as is the case with calcium aluminate sulfate precipitates.

These methods are described in EP-Al-250626.

In a particularly advantageous embodiment of the process according to the invention, the residual arsenic concentration in the effluent can be reduced to 0.5 m
g/N or less, but in this case, pretreated wastewater, especially treatments (A2), (C2), (I1)
or NV) is contacted with an ion exchanger, especially a strongly basic anion exchanger, in the alkaline to neutral pH range.

The strongly basic anion exchanger is a normal crosslinked polystyrene resin with a porous structure and has a quaternary ammonium group as a functional group. Here, the following two types, the active group -N ('CH,>30 [{, type I ridge lipid, and the active group -N ((CI-13)2(C2H.OH))
It can be divided into type H resins that have OH. Type I anion exchange resins have stronger basicity than Type N anion exchange resins, but have lower capacity and significantly inferior regeneration ability, but on the other hand, are less susceptible to oxidation. Type H anion exchange resin also has a stronger mesh during exchange than Type I exchange resin. The main characteristics of these anion exchange resins are as follows. Total capacity: Approximately L. 21 eq. /l wet resin (both types) Effective capacity: 0.4-0.61 eq. /f wet resin (
Type I》 Approximately 0.71eq. /1 Wet Resin (Type ■) The affinity of these anion exchange resins for various anions is in the following order for the OH type.

1 > S O 4 ”- > N O
3- > C r O 4 2- > P O
*3>Ash. ”) Oxale}＞N○2−+ CI
->Formate>Citrate>Tartrate>Phenolate>F->Acetate>H C O 3 ->
H S i O :1>CN->H2BO3->OH Porous anion exchange resins are suitable for use in the method of the invention. Furthermore, porous anion exchange resins have the advantage of high mechanical stability, ease of adjustment, and strong stability even when using colloidal water. Porous exchange resins have a higher loading capacity for organic matter than ordinary resins, and are also easier to wash out during recycling. The present invention is also advantageous in mixed bed ion exchange, where cation exchange resins and anion exchange resins are simultaneously placed in the same apparatus. Since both resins have different densities during regeneration, they can be separated from each other by being rolled up under hydraulic pressure.

Both separated resins can be regenerated and, after regeneration, returned to the mixed bed again, for example by means of compressed air.

You may insert a replacement cartridge. Compared to desalination in separate exchange beds, mixed-bed desalination has the advantages of very constant water quality, near-neutral p}l, and less washing water.

Regeneration of the ion exchange resin is carried out in the usual manner until the loading limit is reached.

Strongly basic anion exchange resins require large quantities of NaO I-1 to convert to OH type 1, typically 4 to 5
A presentation of 200-400% in the form of a % solution is required.

In the present invention, when mixed bed ion exchange is used, it is particularly advantageous to use a chloride type anion exchange resin and an H1 type cation exchange resin. This is because hydrochloric acid can be used as the only regenerating agent for 19.

In the method according to the invention, the adsorption separation of arsenic is carried out by contacting the wastewater with activated carbon. Activated carbon with certain properties is commercially available.

Adsorption of arsenic from wastewater is carried out in treatment (C1) by adding powdered activated carbon to the wastewater or by contacting the wastewater with a fixed bed of activated carbon (FesL)]ett). These methods include treatment (C1) and (
Both C2) can be implemented.

The use of a fixed bed of activated carbon is advantageous in the present invention due to technical aspects of the process and better regeneration.

Activated carbon regeneration is carried out in a well-known manner.

Thermal regeneration of the used activated carbon efficiently recovers the adsorbed arsenic.

The precipitated product or solid from treatment (A2), (C2), (n) or (IV) is preferably washed with optionally pH-adjusted residue, water. At this time, the wash water can be returned to the untreated wastewater. The precipitated products or hardwoods, especially those from process (A2), can be pressed and rendered worry-free in this way. This method is also effective for methods (n) and (IV). Similarly, the regenerating solution from treatment (B2) is added to the treatment! It is advantageous to return to the arsenic precipitation stage of (A1) or the arsenic adsorption separation stage of treatment (C1). It is also a good idea to separate the arsenic in the regenerated liquid from the 71st station (B2) in the form of sparingly soluble arsenic compounds, such as arsenic sulfide. In this case, the obtained solution can be returned to the arsenic precipitation stage of treatment (A1) or the arsenic adsorption separation stage of treatment (C1).

This liquid can also advantageously be recycled as a regeneration liquid.

Masaaki Moto's method uses compounds of calcium and magnesium, and especially their salts. A good suitable calcium monomer is calcium hydroxide. As magnesium compounds, magohydroxide and sium are excellent.

In addition, as magosium compounds, magnesium salts, especially magnesium chloride, are used in treatment (A1).
Are better.

For the device according to the invention, it is advantageous if the storage tanks for the magnesium alloy and the calcium compound are combined into only 19 storage tanks. From there, calcium and magnesium compounds can be fed to the precipitation reactor in a given molar ratio. It is likewise advantageous to combine the oxidation and settling reactors and the subsequent separator.

In some cases, the activated carbon fixed bed reactor is preferably equipped with regeneration equipment capable of not only regenerating the activated carbon but also recovering arsenic desorbed therefrom. If prepared for processing, it can be combined with a lime milk or calcium aluminate reservoir;
It is advantageous to have a further 19 precipitation reactors which can also be used for p T-1 regulation. This precipitation reactor has one more
9 separator and is used for precipitation of calcium sulfate or calcium aluminate sulfate as described above. In this case, the position of this precipitation reactor and the following minute reactor are:
Preferably before the oxidation and precipitation reactors or between these and the adsorption reactor or subsequent ion exchanger.

The separator of the present invention is a precipitation reactor or a centrifugal separator.

The general flow of the apparatus of the present invention will be explained using FIGS. 1 to 4. This allows the method of the invention to be carried out very well.

In FIGS. 1-4, the individual treatments have the same characteristics as previously described.

Each number has the following meaning.

1, oxidation and precipitation reactor 2, acid 1 shavings storage tank 3, calcium (arsenate storage tank 4, magnesium compound storage tank 5, ITII regulator 6, precipitated calcium magnesium arsenate portion) Minutes for one,!J vessel 7, adsorption reactor 8, ion exchanger 9, precipitation reaction for precipitating sulfate as calcium sulfate or calcium aluminate sulfate 10, storage tank for milk of lime 11, calcium aluminate Storage tank 12, p I{regulator 13, ia1M unit 14, compressor 15, waste water supply pipe Figure 1 shows the separation of sulfate and, in some cases, heavy metals by precipitation, and the separation of arsenic by ion exchange. 1 shows an apparatus according to the invention for separation;

These devices operate with a discontinuous supply of wastewater.

The final concentration of As is 0.3 mg/N or less.

FIG. 2 likewise shows an apparatus according to the invention for arsenic separation in discontinuous operation. In this case, As (III
) to As(V), first of all the calcium magnesium arsenate as well as the sulfate and optionally heavy metals are precipitated and separated (At, A2). Then, in order to further reduce the sulfate content in the wastewater, sulfate precipitation and separation ([[I.I'/) are connected. After ion exchange (B1), the residual concentration of arsenic is 0 in this case as well.
．． It is below at 3 mg/l.

FIG. 3 shows an apparatus according to the invention for arsenic separation and wastewater conditioning in continuous operation. In treatments (I) and (ff), C
a SO < Separation of sulfate is carried out. This leads to the precipitation of arsenic and compensating metals in treatments (A1) and (A2). Further proceed to the sulfate branch in the form of calcium aluminate sulfate of treatment ([[[)(It/). The final purification is carried out again in the ion exchanger of treatment (B1).

No. 412I at the top shows another 19 devices of the present invention for continuous operation of wastewater treatment. In this case, first of all, Fjg. acid treatment l, ■), followed by calcium magnesium arsenate (treatment AI, A2) to remove most of the arsenic.
) and is separated by precipitation. Further treatment (I[1)
and MV) followed by sulfate precipitation followed by final purification in an ion exchanger (Tokioki B1).

An adsorption reactor 7 may be used instead of the final purification using an ion exchanger.

The oxidation and precipitation reactor 1 is a stirred tank with an outlet in the lower part which can in particular be connected to a sludge collection pipe of the precipitation product. The oxidation and precipitation reactor 1 can be connected by conduits to an oxidizing agent storage tank 2, a calcium compound storage tank 3 and a magnesium compound storage tank 4 (Figure 4). Furthermore, it is equipped with a pto-adjusting device 5, which allows pI{control or pH adjustment by introducing appropriate reagents and corresponding storage tanks.

The oxidation and precipitation reactor 1 continues into a separator 6 where the precipitated calcium magnesium arsenate is separated from the waste water. The separator 6 can be connected to a sludge collection pipe. The separator is in particular a settling reactor. The sludge containing pollutants is usually dehydrated and becomes safe.

The adsorption reactor 7 is in particular equipped with a fixed activated carbon bed and a regeneration "A" station, with which the activated carbon can be regenerated and the adsorbed arsenic can be recovered. or as a supplement, processing\ffi(I
1) or after treatment (A2). This can also be provided in place of the oxidation and precipitation reactor 1.

The adsorption reactor 7 is further followed by another precipitation reactor 9 of essentially the same type as the oxidation and precipitation reactor 1, in which calcium sulfate is removed from the waste water after pH adjustment in the pi→■ reactor 12. and/or cause precipitation of calcium aluminate phosphate. For this purpose, a precipitation reactor 9 is provided, in particular in a conduit, a storage tank 10 for milk of lime as well as a storage for calcium sulfate f'! It is tied to JLL. The precipitation reactor 9 has an outlet for the precipitation product in its lower part, which is connected to a sludge collection pipe. Another one in this precipitation reactor 9
9 separators are connected in which complete separation of the precipitated products takes place. This divider is also connected with a collection tube.

In the ion exchanger 8, at least residual arsenic, particularly in the anion form, is separated. The ion exchanger 8 is in particular an anion exchanger and a mixed bed ion exchanger.

After regeneration, the regenerated material in the ion exchanger 8 is returned to the process.

As shown in FIGS. 2, 3 and 4, a thickener 13 and a press 14 are provided for the preparation of the sludge, in particular a press overchamber.

The device according to the invention is also advantageously operated by a central control or regulating facility, such as is found in particular in a microcomputer system. monitoring and collecting the signals at a central 1'f location, where corresponding locations of the device are manipulated according to a given program or process model.In this way, the method according to the invention This can be done automatically.The most important thing is to control the return of Suranoji.

Example The invention will now be explained in more detail based on examples.

Similar experiments are also listed for reference.

A wide variety of industrial wastewaters (wastewaters I to ■) and two synthetic wastewaters (synthetic wastewaters I and ■) were used in the experiments.

Industrial wastewater is sourced from various acid polishing processes in glass factories. They contain the same components but differ in the concentration of individual substances, especially those that increase in concentration during the circulation process. Preliminary demonstrations have shown that these wastewaters become very difficult to handle when the alkali content is high, especially when the Na and K content is high. For this reason, such wastewater was selected, taking into consideration whether it is easy to handle, normal or difficult to handle.

The composition of the wastewater used before treatment is shown in Table 2.

(Left below) Table 2 * Added as F** Added as HzSiFs Unquantifiable or not added In this study, As (II1) or As (V) was extracted from solution by various precipitation reactions or by adsorption.
Alternatively, we conducted research on separation by ion exchange.

All arsenic quantification was performed using atomic absorption spectroscopy. (
Graphite method (N i / As; analysis error, 1-5% depending on concentration) The addition of F1 and H2SIF6 confirmed the harmful effects of arsenic in a complex bond. However, no interference with precipitation reactions or arsenic adsorption was observed. The addition of surfactants was also used to determine whether surfactants interfere with the precipitation of calcium magnesium arsenate. However, in this case as well, no negative effects of such addition were observed.

First Comparative Example: Hydroxic acid (
P. Arsenic was precipitated using calcium (Ca(OH)z).

The results obtained are summarized in Table 3.

In addition to the concentration, the content of arsenic remaining in the arsenic is determined by
The degree of As separation, also expressed as base l· with respect to the initial amount of arsenic (I00%) in the wastewater used, represents the percentage of arsenic separated with respect to the initial As content in the wastewater.

In the experiment carried out with Table 3, Comparative Example 2 wastewater ■ (containing arsenic, 16.9 mgy! - see Table 4), arsenic was precipitated with Ca (OH) 2, but in this case, the precipitate was As (I [ ＞As (
V) was carried out without acid exposure (Experiment A), or with alkaline oxidation (Experiment B), or with acidic oxidation (Experiment C).

For precipitation with C' a (OH) 2, the pH
(Ii was set to 9.0. The precipitation was 45°C at 25°C.
Go in minutes? Ta.

In Example B, an oxidizing agent I1 and 0 was added to an alkaline solution. In contrast, in experiment C, acidification was carried out in an acidic solution, followed by raising the pH to 9 for precipitation.

These experiments were conducted in Wastewater II! 35゛1 of various amounts per hit
δH20. This was done by adding water. The results obtained are the fourth
It is summarized in the table. The percentage of residual arsenic content is again '' with respect to the initial arsenic content (I00%).

The degree of separation of arsenic expressed in basis centage is complementary to the residual arsenic content expressed in percentage.
It corresponds to the percentage of arsenic separated to the arsenic content of JN. (Margins below) Table 4 These results show that the oxidation of As(V)' from As(I1) significantly improves the arsenic content in each case (from about 50-60% to about 74-80%
). It is also clear that there is no big difference between oxidation in alkaline and acidic conditions. Furthermore, it is clear that the amount of H 2 O 2 used has no significant effect.

Furthermore, even if the reaction time was extended beyond 45 minutes, no better results were obtained. Adding an oxidizing agent H202 is advantageous due to the acidic pH. This is because if sufficient reaction time is allowed, the oxidizing agent will not reach the ion exchanger.

First Example and Third Comparative Example The first example shows steps (A1) and (A1) of the method of the present invention.
According to 2), arsenic is separated from wastewater by precipitating poorly soluble calcium magnesium arsenate using a compound of calcium and magnesium simultaneously as a precipitant.

The third comparative example concerns precipitation with only a calcium compound. As the calcium f-hyde compound, milk of lime (C a (O}{>23) was used.

One example of magnesium is M g ( O H
) 2 was used.

The ratio of the amount of precipitant is Ca:Mg:AsO+ =3:3
・It is 1.

The shoulder is settled at 25°C for 30 minutes at p+-110.5 or higher. In the experiment, wastewater ■ and ■ (
(See Table 4), wastewater ■ was used as an easy-to-handle wastewater. First, a certain amount of chemical is added to the acidic raw wastewater to increase the pH value to 10.5 or more, and then the fS. The results obtained are summarized in Table 5.

(Left below) From the results in Table 5, it can be seen that the method of the first example of the present invention, which uses a combination of calcium and magnesium compounds, is different from the method of the third example, which uses only the calcium compound and is carried out under the same conditions.
The results of the 6 arsenic separations, where the precipitation results are significantly improved compared to the comparative example, are shown in parentheses below the numerical values of the first example, as compared to the third comparative example. The extra arsenic separation achieved is shown in percent.

Second and Third Examples and Fourth Comparative Example These experiments were carried out on four different wastewaters in which pure calcium arsenate was precipitated by the method of the present invention (the fourth example).
Comparative Example), the case where the wastewater is not oxidized (Second Example), and the case where the wastewater is acidified with H 202 in advance (Third Example).
This is a comparison of precipitation in the presence of calcium and magnesium compounds.

Acid f-hi was performed in the acidic rlH range.

As a calcium r arsenide, (a (OH)2
was used. Mg (01
-1): was used for one history.

Wastewaters ■ and ■ are ordinary wastewaters that are easy to handle, and wastewaters ■ and ■ are wastewaters that are difficult to handle. The results obtained are summarized in Table 6.

(Left below) From the results in Table 6, it is clear that the methods according to the present invention in Examples 2 and 3 are more effective than precipitation of calcium arsenate (Fourth Comparative Example), and moreover, in wastewater that is easy to handle. Similarly, it can be seen that a large improvement can be seen in the case of difficult-to-handle wastewater.6 Furthermore, when arsenic in wastewater is oxidized to As (V), in Example 3, there is a significant improvement compared to Example 2. can be seen.
In the column for the degree of separation of arsenic, in the second and third examples,
The extra degree of arsenic separation achieved compared to the fourth comparative example is shown in parentheses.

Fourth Example This example concerns adsorption and leakage of arsenic from wastewater by contact with activated carbon, treatment (C1) of the method of the present invention.
This corresponds to <C2).

In the experiment, industrial wastewater containing high gL acid ions (waste/kV
) was used.

First, Ca (OH) 2 was added to this wastewater and the pH was adjusted to 3.0 for 30 minutes to form CaSO. 2 salts were precipitated. The settled sludge was separated.
The obtained primary purified wastewater has an arsenic content of 335 mg
／／! However, after adjusting the p I-1 by adding Ca (OH)2, the arsenic content was measured after various types of activated carbon were soaked in fJII for 30 minutes.The obtained results were as follows. , shown in Table 7.

These results show that, unlike the results of the literature cited at the beginning, adsorption and separation of arsenic by activated carbon is very effective, and the arsenic separation rate is very high depending on the amount of activated carbon (for example, 15 g of activated carbon per 11 wastewater is 97. 6r.:;) can be obtained.

Furthermore, adsorption experiments revealed that the adsorption efficiency of arsenic onto activated carbon is practically unrelated to the pH value of the medium in contact with the activated carbon. Furthermore, there was no relationship between separation efficiency and whether or not activated carbon was separated at the same time.

From an economic point of view, activated carbon adsorption or separation is
It is most advantageous to use an activated carbon fixed bed filter which can be regenerated.
1) and (C2) can be implemented simultaneously.

1 kg of activated carbon can absorb 1.2 to 1.6 g of arsenic, so adjust the amount of activated carbon you add accordingly.
The fixed bed filter may also be of a simple style.

Fifth Embodiment The second embodiment is an example of an excellent embodiment of the method according to the present invention. In this process, the residual arsenic may or may not be precipitated in the form of calcium magnesium arsenate, and the sulfates contained may be precipitated (9"9 CP-
A 1 8 6 L O 8 8 7 6 ) L is carefully separated using an ion exchanger. A mixed bed ion exchanger was used here.

160g (200+n+2) of ion exchange resin,
Place in a glass tube (2 cm diameter) with a stopcock at the end. The loaded height is 80cm. Sampling is performed by taking a precisely fixed amount at the outlet of the glass tube. The arsenic content was determined using the atomic absorption spectrometry method as described above. Experimental strip 1'F and analytical flow velocity: 1. OL'/h Bed exchange 6 times (Fach) (BeLtaustausch)pi {Initial fi
iI: 11.5 SO. Initial value: 50 mg/j' As initial value: 14 mg/N Conductivity (κ) initial value: 2.3 mS/crr+21 treatment (=81/l ion exchange resin) Final pH of residue: 6.5 SO. :Undetectable conductivity>:2.1μS/c mAs
: 2.5 μg/r The above-mentioned withered fruit indicates that complete salting has been carried out. Along with arsenic, the ions taken up in all pond ion exchanges are also being exchanged. This shows that the water quality is good and pure, with very little conductivity. H as a regenerant for both ion-exchanged tA resins in the mixed bed.
CI! In this case, there is a possibility of reusing arsenic. In this way, the anion exchange resin (I
One type of cation exchange resin can be changed to H type.

SIXTH EXAMPLE This example, as in the fifth example, removes the sulfate to a considerable extent by precipitating it in lime pits and subsequently precipitating it with calcium aluminate. Value 1 1. 4 ~1 1. This is concerned with separating residual arsenic from primary purified wastewater having a concentration of 7.

In Jishun, we used Type I, a Ce type I, strongly basic anion exchange {A fat.

In the experiment? I Ma's {Cooking fat presentation (50.75 or 200
g) and packed into columns with a diameter of 2 cm. The flow rate and the resulting bed exchange were varied. Regeneration was carried out in the form of a 5-8% solution with 200 g HCIIOO%/l ion exchange resin for 40 minutes. The regenerant was passed through the ion exchange bed in the flow direction.

The results obtained are summarized in Table 8.

These results indicate that arsenic does not suddenly appear at a liquid volume of 71, which corresponds to a 1 1 21 /e ion exchange resin. This means that approximately 2.5 gAs
/1 corresponds to the capacity of the ion exchange resin. The lower the flow rate, the better the purification.

At high sulfate concentrations, the affinity of sulfate ions comes before arsenate ions (see above), resulting in a corresponding decrease in acceptance. Therefore, the high sulfate content must be removed in the next step, which can be done in a straightforward manner according to the method described above.

In the next experiment. The loading capacity of a strongly basic anion exchange resin used for one hour was investigated.

Conditions pH: 11.5 Sot: 20mg/& Conductivity (κ) + 2.0mS/cm 4 to S initial concentration: 13.4mg7i' Flow rate: 1.21/h Bed exchange = 8.5 times Used solution Amount = 351 As final concentration: 10 ~ 119 ppb Conductivity (κ) final: 2.30 mS/cm resin
Amount: 100g Column size: Height 760mm; Diameter 1.8cm Calculating from the above results, the load volume i (effective volume capacity) is 4.
1-4.5 g As/l ion exchange resin, which corresponds to approximately 0.25 meq AsO'-/1 ion exchange resin. If the wastewater has an initial content of 10 mg A s / 1, at least 4001 wastewater is purified by 11 ion exchange resins. As is clear from the above results, a strongly basic anion exchange resin can reduce the arsenic content in wastewater to the PPb range. Purification results are essentially related to the arsenic oxidation stage, flow rate, and arsenic concentration. Actually, 4.5gAs/i! The high load capacity of ion exchange resin can be easily achieved.

Anion exchange resins are particularly used in the chlorine form. The chloride freed by ion exchange can be advantageously used as a control substance for monitoring or regulating the ion exchange process. By reusing the reclaimed liquid, valuable raw materials can be recovered and also returned to the manufacturing process. Practically 100% of the arsenic can be separated and obtained from the regenerated solution as a sulfide precipitate. You can restore it like this,
It is also possible to use the pond method for one cycle to produce some sedimentation.

Effects of the Invention The subject of the present invention concerns a new type of concept for the removal of arsenic from wastewater, by means of which it is possible to eliminate this important environmentally harmful substance to a significant extent on a technical and industrial level for the first time. They can then be removed from wastewater in very economical and chemically simple ways and reused in manufacturing processes.

Chromate and phosphorus in the arsenic pond! ! ! Other chemically similar anions, such as salts, can also be removed from wastewater.

The inventive concept has the following particular advantages:

The method of the present invention can be applied even to highly acidic wastewater, which is extremely difficult to handle.
Can be used as an official.

For example, 10 mg from the acid polishing process in the glass industry.
/1 or more arsenic, and precipitation with Fe, Ca, etc., can only separate arsenic to a very insufficient extent by precipitation in the form of calcium magnesium arsenate (A s <
2 mg/'l) and subsequent activated carbon adsorption, it is possible to reduce the amount of residual arsenic to less than 1 mg/'l, and the activated carbon can also be easily regenerated.

By combining precipitation in the form of calcium magnesium phosphate and/or adsorption separation of arsenic by ion exchange, the residual arsenic content can be reduced to a range of PPb below 0.3 mg/1, and in some cases even lower. Arsenic can be easily and quantitatively precipitated as sulfide from the regenerated solution of ion exchange resin. The regenerated solution can be returned to the calcium precipitation step or concentrated. The method concept according to the invention can also be used for solutions with high FiR salt content. By precipitating with calcium at about pH' 3, most of the sulfate can be stripped off without precipitating the arsenic. This precipitate, after washing the C a S O + sludge with water, may be treated as simple waste, construction waste or household waste, as the case may be. Further precipitation in the form of calcium aluminate effectively reduces the residual SO
, can be removed.

By precipitating arsenic in the form of calcium magnesium arsenate, most of the arsenic (approximately 50-80% in bulk)
can be selectively precipitated.

This sediment can be treated as special waste or recycled by pond method.

Surfactants are present in considerable amounts in most wastewaters, but sulfate precipitates. Crushing also does not interfere with the precipitation of calcium magnesium arsenate.

[Brief explanation of the drawing]

FIG. 1 shows an apparatus according to the invention for the separation of sulfates and optionally heavy metals by precipitation and arsenic by ion exchange; FIG. FIG. 3 shows an apparatus according to the invention for arsenic separation and wastewater conditioning in continuous operation,
FIG. 4 shows another apparatus according to the invention for continuous operation of wastewater treatment. 1 oxidation and precipitation reactor, 2... oxidizing agent storage tank, 3
Calcium (arsenic compound storage tank), 4. Magnesium (arsenic compound storage tank, 5. pH regulator, 6. Separator for burying precipitated calcium magnesium arsenate,
7... Adsorption reactor, 8... Ion exchanger, 9...
Precipitation reactor for precipitating sulfate as calcium sulfate or calcium aluminate sulfate, 10. Storage tank for milk of lime, 11. Storage tank for calcium aluminate, 12.. pH regulator, 13. ...Dark 4! Vessel, 14...
・Expressor, water supply pipe agent for 15 wastewater Patent attorney Keiichiro Nishi

Claims (1)

[Claims] 1. In each of the following steps (A1), calcium and magnesium compounds are added to the wastewater at a pH value of 2 to 12, preferably 9 to 11, and a precipitation time of about 10 to about 60 minutes, preferably about 30 minutes. (A2) separation of the calcium magnesium arsenate, and/or (B1) treating the wastewater with an ion exchange resin, preferably a strongly basic one. anion exchange resin and a pH value of 2 to 12, preferably 7 to
11.5 and, if necessary, (B2) regenerating the ion exchange resin after reaching the loading limit; and/or (C1) contacting the wastewater with activated carbon at a pH value between 2 and 11, preferably 2.
A method for separating arsenic from wastewater, characterized in that it comprises adsorbing and separating arsenic by contacting the wastewater with (C2) separating the adsorbed activated carbon alone or together with a precipitated product. 2. As for the wastewater to be treated in step (A1), (B1) or (C1), the As(I
II) with the addition of an oxidizing agent, preferably CaO_2, MgO_2 or H_2O_2, and AsO_4^ in an acidic pH range.
Claim 1 characterized in that it is oxidized to 3^-
The method described in section. 3. Adding Ca(OH)_2 to the wastewater before step (A1), (B1) or (C1) or after step (A2), (B2) or (C2) in each of the following steps (I) precipitating CaSO_4 by precipitating CaSO_4 before step (A1), preferably at pH 3±1, or before step (B1) or (C1), preferably at pH 3±1;
3±1 or 8.0 to 11.0, and (II) separating precipitated CaSO_4 and optionally precipitated heavy metal hydroxides, and/or (III) highly reactive aluminum oxide and/ Or add calcium aluminate to the wastewater and Ca(OH)_
(IV) separating the precipitated calcium aluminate sulfate from the wastewater; (IV) separating the precipitated calcium aluminate sulfate; Claim 1 or 2, characterized in that sulfate ions contained in the sulfate ions are separated.
The method described in section. 4. In step (A1), the magnesium compound is added in such an amount that magnesium hydroxide is precipitated until the pH is in the alkaline range.
The method described in Section 3. 5. The method according to claims 1 to 4, characterized in that calcium hydroxide is used as the calcium compound and/or magnesium hydroxide is used as the magnesium compound in step (A1). 6. In step (A1), a mixture of calcium and magnesium salts is used, optionally in the presence of Ca(OH)_2, according to claims 1 to 4. Method. 7. Process according to claims 1 to 4, characterized in that in step (A1) a magnesium salt, preferably magnesium chloride, is used as the magnesium compound. 8. By contacting wastewater with activated carbon in a fixed bed,
8. A method according to claim 1, characterized in that steps (C1) and (C2) are carried out together. 9. The method according to claims 1 to 7, characterized in that in step (C1) powdered activated carbon is added to the wastewater. 10. The method according to claims 1 to 9, characterized in that the adsorbed activated carbon from step (C2) is regenerated by heat to recover the arsenic compound. 11. Step (A2), (C2), (II) or (I
The method according to claims 1 to 10, characterized in that the precipitated product or solid from V) is washed with water and, if necessary, after pH adjustment, the wash water is returned to the raw wastewater. . 12. Transfer the regeneration liquid from step (B2) to step (A
12. The method according to claim 1, wherein the method is returned to the arsenic precipitation step of step (1) or the arsenic adsorption separation step of step (C1). 13. The method according to claims 1 to 12, characterized in that a chlorine-type anion exchanger is used in step (B1). 14. In step (B1), chlorine type anion exchanger and H
A mixed bed ion exchanger having a type of cation exchanger is used, and in step (B2) the ion exchanger is regenerated using hydrochloric acid as a regeneration agent. The method according to paragraph 13. 15. The method according to claims 1 to 14, characterized in that in step (I), the pH is kept constant at 3±1. 16. The method according to claims 2 to 15, characterized in that As(III) contained in the wastewater is oxidized in a precipitation reactor used for the precipitation treatment beforehand or immediately afterward. 17. Precipitating arsenic, preferably in the form of arsenic sulfide, from the regenerated liquor from step (B2), separating the arsenic sulfide, and passing the resulting solution to the arsenic precipitation stage of step (A1) or to step (B2). 17. The method according to claim 1, wherein the method is returned to the arsenic adsorption separation step of C1) or reused as a regenerating solution. 18. The configuration according to the order of the following main reaction routes: oxidation and precipitation reactor for precipitating calcium magnesium arsenate, which is optionally equipped with an oxidizer storage tank in a conduit;
connectable with a storage tank for calcium compounds and a storage tank for magnesium compounds and with a pH regulator, and a separator for separating precipitated calcium magnesium arsenate from the wastewater, and/or for contacting the wastewater with activated carbon. adsorption reactor, and/or
An apparatus for carrying out the method according to claims 1 to 17, characterized in that it comprises an ion exchanger or an ion exchanger. 19. Device according to claim 18, characterized in that the storage tank for calcium compounds and the storage tank for magnesium compounds are combined into a single storage tank containing calcium and magnesium compounds. 20. Apparatus according to claim 18 or 19, characterized in that the oxidation and precipitation reactor and the separator are integrated together. 21. The apparatus according to claims 18 to 20, wherein the adsorption reactor is an activated carbon fixed bed reactor equipped with a regenerator capable of recovering desorbed arsenic. 22. The apparatus according to claims 18 to 21, wherein the ion exchanger is an anion exchanger or a mixed bed ion exchanger having a regenerator. 23. Another precipitation reactor, which can be connected by conduits to a reservoir of milk of lime and a reservoir of calcium aluminate, and is equipped with a pH regulator, followed by precipitated calcium sulfate and/or aluminate. Contains a separator for separating calcium sulfate, in which case the arrangement of the precipitation reactor and separator is before the oxidation and precipitation reactor, between the oxidation and precipitation reactor and the adsorption reactor, or between the adsorption reactor and the ion 23. Device according to claim 18, characterized in that it is between exchangers. 24. Claim 1, characterized in that the separator and/or separator is a precipitation reactor or a centrifugal separator.
The device according to items 8 to 23. 25. Wastewater containing arsenic, sulfates and heavy metals, preferably lead-containing wastewater from acid polishing processes and polishing wastewater in lead glass and crystal glass production, sulfate-containing wastewater from flue gas desulfurization equipment and energy storage industry. and the first claim characterized in that it is used for wastewater from microchip manufacturing.
The method described in items 1 to 17.